Fourier 300 mhz spectrometer

Melting points (uncorrected) were determined in open capillary on an OptiMelt melting point apparatus (MPA 100, Stanford Research System, Inc., Sunnyvale, CA, USA). The progress of the reaction was monitored by TLC on silica gel 60 or 60F₂₅₄ plates (Merck, Darmstadt, Germany) eluted with the solvent systems: I dichloromethane-methanol, 9:1, II dichloromethane-methanol, 95:5, III dichloromethane-methanol, 4:1. Spots developed in UV and with 15% H₂SO₄ in MeOH (heating at 110 °C, 10 min). IR spectra were recorded on FT-IR-100 Perkin Elmer spectrometer (Perkin Elmer, Shelton, CT, USA), in solid phase by ATR and frequencies were expressed in cm⁻¹, with the following abbreviations: w = weak, m = medium, s = strong, v = very, br = broad. ¹H-NMR and ¹³C-NMR spectra are recorded on Bruker Fourier 300 MHz spectrometer (300 MHz for ¹H and 75 MHz for ¹³C, Karlsruhe, Germany), or Bruker Avance III 500 MHz spectrometer (500 MHz for ¹H and 125 MHz for ¹³C), spectrometer chemical shifts are given in ppm relative to TMS as internal standard. Complementary spectra: 2D-NMR and decoupling were done for the correct assignment of NMR signals. The numbering of the atoms in the compounds is presented in schemes. Diol 2 was obtained by sodium borohydride reduction of the keto group of compound 1, as previously presented [36 ], having mp 116–117.2 °C, [α]_D = 11.3° (1% MeOH).

NMR analysis of mixtures of lipids or pure lipids were performed in a FOURIER-300 MHz spectrometer (B₀ = 7.05 T, Bruker, Germany) at 23°C and 300.19 MHz using deuterated chloroform (CDCl₃, Sigma-Aldrich, St. Louis, MO) as solvent. For all the pulse sequences, packages from Bruker were used. 700 μl of sample solutions containing 2–8 mg of purified lipids were placed in a 5 mm-diameter NMR tube (in such a way the length of the tube filled with the liquid sample occupied approximately 4.5 cm long). All spectra were recorded with sample rotation and the chemical shifts are expressed in δ scale (ppm), referenced to the residual signal of chloroform (7.26 ppm) [62 (link)]. Signals were characterized as singlet (s), doublet (d), doublet of doublets (dd), triplet (t) or multiplet (m). The software TopSpin was employed to acquire the spectra and all data were analysed thought the software MestreNova. The assignments were performed mainly according to [40 –42 ,63 ]. The peaks corresponding to solvent non-deuterated (>1%) and trace impurities were identified following the method described in [64 (link)].